Generics in Java 5

Generics in Java 5

Lots of New Language Features in Java 5…

The new features work together…

…autoboxing…

How did that work?

How does it work now?

Common operations are now typesafe

Customise Collection Classes

Customise Collection Classes (continued)

Reveal implicit type requirements of interfaces

Add control over argument validation

Add control over argument validation (continued)

But Java has always been able to do that!

Arrays are covariant

Covariance requires RTTI

Generics can’t have RTTI

Erasure (continued)

So generic classes can’t be covariant

How will we do without covariance?

How will we do without covariance? (continued)

Wildcards (continued)

Using a wildcard type restricts access

Using a wildcard type restricts access (continued)

Bounded wildcards can work together

Bounds work with type variables too

Erasure produces some surprises

Erasure produces some surprises (continued)